TWI547334B - Planar light source device, light guide for use therein, and method for manufacturing the same - Google Patents

Description

Surface light source device, light guide for surface light source device and method of manufacturing same

The present invention relates to an edge light source type surface light source device, and a light guide body for constituting the surface light source device, and more particularly to a surface light source device having a feature of a light exiting structure formed on a main surface A light guide, a method of manufacturing the same, and a surface light source device using the light guide.

The surface light source device using the light guide of the present invention is suitable for use as, for example, a backlight of a liquid crystal display device such as a screen for carrying a personal computer or the like, or a display unit such as a liquid crystal television.

The liquid crystal display device basically consists of a backlight and a liquid crystal display element. As a backlight, a backlight of an edge light emission type is often used from the viewpoint of downsizing of a liquid crystal display device. In the edge light-emitting backlight, at least one end surface of the rectangular plate-shaped light guide is used as a light incident end surface, and a linear or rod-shaped primary light source such as a straight tube type fluorescent lamp is disposed along the light incident end surface. Or a point-like primary light source such as a light emitting diode (LED), such that light emitted from the primary light source is incident on the light incident end surface of the light guide body and introduced into the light guide body, and then the light is self-induced A light exit surface that is one of the two main surfaces of the light guide is emitted. The light emitted from the light-emitting surface of the light guide is diffused by a light-diffusing element such as a light-diffusing element such as a light-diffusing film disposed on the light-emitting surface, and a light deflecting element such as a cymbal, and is deflected in a desired direction. Light is also emitted from the back surface of the other of the two main surfaces as the light guide. In order to return the light to the light guide body, a light reflecting element such as a light reflection sheet is disposed opposite to the back surface.

A light-emitting mechanism that is an optical functional structure for appropriately emitting light that guides light in the light guide body is formed on the light-emitting surface or the back surface of the light guide. As the light-emitting means, for example, a rough surface which is moderately roughened or a micro-concave structure such as a lens row forming surface in which a plurality of lens rows are arranged can be used.

In order to form such a fine concavo-convex structure, there is known a method of press-molding a light-transmitting material such as an acrylic resin using a molding apparatus, and the molding apparatus includes a molding die member including a shape transfer surface formed by sandblasting or cutting. It is formed (refer to Patent Document 1 and Patent Document 2).

Further, a method of directly processing a light-transmitting material to form a light-emitting means is known. For example, Patent Document 3 discloses that a surface of a light guide body is irradiated while scanning a laser beam, thereby forming a plurality of grooves. It is used as a light guide body with a fine uneven structure.

Further, a method of using a light-scattering agent or a bubble as a light-emitting means is also known. For example, Patent Document 4 discloses a light-guide body including a foam which is foamed by the application of radiation energy and thermal energy. .

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] International Publication No. 2005/073625

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-266830

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2007-87638

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2006-155937

When a light guide having a fine uneven structure is produced by press molding as disclosed in Patent Document 1 and Patent Document 2 above, it is necessary to produce a mold member for molding. Further, when the configuration of the fine concavo-convex structure to be formed on the main surface of the light guide is changed, it is necessary to replace the mold member for molding, which is troublesome in operation and takes time, and the manufacturing efficiency may be lowered.

Further, when the micro concave-convex structure transfer surface is formed on the molding die member by sand blasting, in order to obtain uniform light emission on the entire light guiding surface of the light guiding body, the light is incident away from the light close to the light incident end surface. The area of the end face (1) is more strongly or (2) more densely sandblasted. In this case, the blast marks (1) in the region far from the light incident end surface are deeper or (2) overlapped than the blast marks in the region close to the light incident end surface, and the inclination angle of the light receiving surface of the light emitting mechanism changes. A region of the light guide body that is away from the light incident end surface and a region that is close to the light incident end surface changes in the light emission direction from the light exit surface.

In addition, when a micro concave-convex structure transfer surface including a plurality of concave portions having a smooth surface (for example, an arrangement of a plurality of lens rows) is formed on a molding die member by cutting or the like, the inclination angle of the concave portion is set to a desired inclination. The angle by which the light emission direction of the light exit surface of the light guide body can be easily controlled. However, in this case, the distribution of the light emission angle from the light guide light exit surface becomes a peak-shaped distribution concentrated at a narrow angle, and becomes a narrow viewing angle. As a result, when the light guide body and the various optical sheets are combined to form or form a surface light source device, the concave portion provided as the light emitting means emits light more strongly than the peripheral portion, and therefore, in order to make it easy to see through, Further, it is necessary to form the concave portion in a fine and dense manner by the high-quality surface light source device in which the entire light guiding surface of the light guiding body is uniformly emitted.

Further, since the conventional fine concavo-convex structure as described above diffuses light only according to the surface shape of the main surface of the light guide body, the diffusibility is insufficient, and when it is required to increase the angular distribution of the emitted light from the surface light source device, it is necessary. A light diffusing element is disposed on the light guiding surface of the light guide.

As a method of enhancing the diffusibility of the light-emitting mechanism portion, Patent Document 3 proposes a method of forming a groove having fine pores on the surface. By using this technique, it is possible to obtain a wider angular distribution of the emitted light than the light guide having a light-emitting mechanism having a smooth surface. However, since the light is diffused only by the fine unevenness on the surface of the groove, the diffusion property is obtained. Not enough.

On the other hand, the light guide of Patent Document 4 realizes light emission based on light scattering formed by the foamed portion. When the light guide is manufactured, it is necessary to add a specific blowing agent. Further, in this technique, the angular distribution of the emitted light can be increased by light scattering in the foamed portion, but the angle of the boundary (boundary surface) between the foamed portion and the other portion cannot be set to a desired angle. Therefore, the direction in which the light from the light guiding surface of the light guiding body is emitted cannot be set to a desired direction.

In view of the above-described technical problems, it is an object of the invention to provide a light guide for a surface light source device having a light exiting mechanism based on a new light diffusing function.

In view of the above-described technical problems, another object of the present invention is to provide a light guide for a surface light source device that can set a direction in which light emitted from a light exit surface is set to a desired direction.

In view of the above-described technical problems, another object of the present invention is to provide a light guide for a surface light source device which can be manufactured without using a molding device using a molding die member.

Still another object of the present invention is to provide a method for facilitating the manufacture of the light guide for a surface light source device as described above, and a surface light source device using the light guide for a surface light source device as described above.

According to the present invention, there is provided a light guide for a surface light source device that includes a light incident end surface, a light exit surface, and a light emitting surface on the opposite side of the light emitting surface. a plate-shaped light guide body on the back surface, wherein at least a part of the light-emitting surface and the back surface is formed with a foamed surface layer in at least a part of the region, and the foamed surface layer contains bubbles and includes the above The cross section of the light exit surface or the normal line of the back surface has a concave shape.

In one form of the invention, the foamed surface layer has a thickness of from 1 μm to 50 μm. In one embodiment of the invention, the diameter of the bubbles contained in the foamed surface layer is from 1 μm to 50 μm. In one aspect of the invention, the region in which the portion of the foamed surface layer is formed includes a dot-like region in one of the light exit surface and the back surface. In one aspect of the invention, the region in which the portion of the foamed surface layer is formed includes a stripe-shaped region in one of the light exit surface and the back surface. In one aspect of the invention, the foamed surface layer and a portion other than the foamed surface layer of the light guide include an acrylic resin.

Further, according to the present invention, there is provided a surface light source device which is characterized in that the surface light source device includes the light guide body for the surface light source device and the light incident end surface adjacent to the light guide body. Formed by a primary light source.

In one aspect of the invention, the surface light source device further includes a light reflecting element disposed adjacent to a rear surface of the light guiding body. In one aspect of the invention, the surface light source device further includes a light deflecting element disposed adjacent to a light emitting surface of the light guiding body. In one aspect of the invention, the light deflecting element includes a light incident surface that is closer to the light guide and a light exit surface that is opposite to the light incident surface, and the light exit surface includes pixels that are arranged in parallel with each other. Formed by multiple arrays.

Furthermore, according to the present invention, there is provided a method for producing a light guide for a surface light source device, which is a method for producing a light guide for a surface light source device. A plate-shaped light guide material including an acrylic plate is produced by a continuous plate making method, and at least a portion of at least a part of at least one main surface of the plate-shaped light guide material is subjected to laser etching. Thereby, the above-mentioned foamed surface layer is formed.

In one form of the invention, the laser used in the above laser etching is an infrared laser.

According to the present invention, the foamed surface layer of the light guide body has an optical effect of causing the light guided light to exit from the light exit surface, and in particular, bubbles are formed only in the vicinity of the surface of the concave portion, and the inside of the bubble contains the refractive index and the light guide body. A gas having a large difference in material can obtain a large light diffusing effect, and thus a light guide for a surface light source device having a light emitting mechanism based on a new light diffusing function is provided.

Moreover, according to the present invention, the light guide for the surface light source device can be produced without using the molding device using the molding die member, and the shape of the foamed surface layer can be easily and quickly changed by changing the processing conditions of the laser etching.

In particular, according to the present invention, since the foamed surface layer is locally present on the inclined surface of the concave portion, a wide viewing angle and a high light-emitting quality can be obtained by scattering, and light can be made by appropriately setting the tilt angle of the inclined surface. The light is emitted in a desired direction. Further, by arranging the concave portion of the foamed surface layer partially on the inclined surface over the entire area of the main surface of the light guide body, the light can be easily emitted in the same direction throughout the entire area. The concave portion in which the foamed surface layer is locally present on the inclined surface is formed by a simple method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a schematic configuration view showing an embodiment of a surface light source device according to the present invention, and FIG. 2 is a schematic partial cross-sectional view showing a light guide body in the surface light source device. As shown in Fig. 1, the surface light source device of the present embodiment includes an LED 22 as a point-like primary light source, a plate-shaped light guide 24 that guides light emitted from the LED, and a light diffusing element 26, The first optical deflecting element 28, the second optical deflecting element 30, and the light reflecting element 32.

The light guide body 24 has the vertical direction in FIGS. 1 and 2 as a thickness direction, has expandability in a direction perpendicular to the paper surface, and has a rectangular plate shape as a whole. The light guide body 24 has four side end faces, and at least one of the at least one pair of side end faces is set as the light incident end face 241, and the LED 22 is disposed adjacent to the light incident end face. The upper surface of one of the two main surfaces substantially perpendicular to the light incident end surface 241 of the light guide 24 is set as the light exit surface 242. In the present embodiment, the light-emitting surface 242 includes a smooth surface (mirror surface). However, the light-emitting surface is not limited thereto, and a light-emitting surface may be provided with a meandering lens shape, a lenticular lens shape, a microlens shape, or the like.

Furthermore, a plurality of LEDs 22 may be provided. In this case, it is preferable that the plurality of LEDs 22 are disposed at a proper interval in a direction perpendicular to the plane of the paper of FIG. 1 so that the directions of the maximum intensity light of the light emitted from the LEDs 22 are parallel to each other. The way to configure.

A light emitting means is formed on the main surface (back surface) 243 opposite to the light exit surface 242 of the light guide 24. The light exiting mechanism includes a foamed surface layer 244 formed in a region of a portion of the back surface 243. The cross section (longitudinal section) of the foamed surface layer 244 in the direction including the normal line of the light exit surface 242 or the back surface 243 has a concave shape.

3 is a plan view of a scanning electron microscope (SEM) showing an example of the foamed surface layer 244, and FIG. 4 is a SEM cross-sectional perspective view thereof. The region in which the foamed surface layer 244 is formed includes a plurality of dot-like regions on the back surface 243. The dot-shaped region has a diameter of, for example, 30 μm to 1000 μm and a depth of 0.1 μm to 500 μm, and the inclined angle α of the slope shown in Fig. 2 is 1° to 70°.

Further, the shape of the region in which the foamed surface layer 244 is formed is not limited to the dot shape as described above, and may be a shape including a stripe-shaped region, that is, a linear or strip-shaped region. In this case, the shape of the cross section (longitudinal section) orthogonal to the extending direction of the stripe is also applicable to the description of the shape of the cross section (longitudinal section) in the case of the above-described dot shape.

The foamed surface layer 244 can be formed by performing laser etching processing using a plate-shaped light guide material containing an acrylic resin plate as will be described later. Then, the foamed surface layer 244 and the portion other than the foamed surface layer of the light guide body 24 contain an acrylic resin.

In the manufacturing method as will be described later, the longitudinal cross-sectional shape (contour) of the foamed surface layer 244 can be changed by the output of the laser, the scanning speed, and the focus position (focus position) of the main surface of the light guide material. The distance is changed.

The foamed surface layer 244 contains a plurality of bubbles, and the inside of the bubbles contains a gas having a large difference in refractive index from the light guide material. Then, the foamed surface layer 244 functions as a non-uniform layer for transmission and reflection of light, and functions as a light diffusion layer in terms of optical properties. Thereby, light incident on the light incident end surface 241 and guided by the inside of the light guide body is diffused and reflected in the foamed surface layer 244, and a part of the light is emitted from the light exit surface 242 at an allowable angle toward the light exit surface. 242, and emerges from the light exit surface.

Since the foamed surface layer 244 as described above is formed in a portion of the light guide back surface 243, the normal direction including the light exit surface 242 (the vertical direction in FIGS. 1 and 2) and the incidence of light are formed. Light having a slightly broad directivity in the in-plane distribution of both of the directions in which the end faces 241 are orthogonal is emitted from the light exit surface 242. Therefore, a light guide for a surface light source device having a wide viewing angle and a light-emitting mechanism portion that is difficult to be recognized and whose quality is easily adjusted can be obtained.

The thickness of the foamed surface layer 244 is preferably from 1 μm to 50 μm, and the diameter of the bubbles contained in the foamed surface layer 244 is preferably from 1 μm to 50 μm.

When the diameter of the bubble contained in the foamed surface layer 244 is too small, the scattering intensity of light propagating in the light guide body 24 exhibits wavelength dependence, and thus is generated in a region close to the light incident end surface 241 of the light guide body 24. A color shift phenomenon in which the hue of the emitted light changes in a region away from the light incident end surface 241. On the other hand, when the diameter of the bubble contained in the foamed surface layer 244 is too large, the surface area of the bubble becomes small, and thus the diffusion efficiency is lowered.

Further, when the thickness of the foamed surface layer 244 is too small, the diameter of the bubbles contained in the foamed surface layer 244 is also necessarily too small, and therefore the description of the case where the diameter of the above-described bubbles is too small is applied. On the other hand, in the case where the thickness of the foamed surface layer 244 is too thick, the above-described description is applied to the case where the diameter of the bubble is too large, and in the case where the diameter of the bubble is appropriate, the emission rate in the foamed surface layer becomes If it is too high, it is difficult to achieve uniformity of brightness in the entire area of the light guide body 24.

Further, when the concave portion is formed by laser etching, the foamed surface layer 244 is partially present in the vicinity of the surface of the concave portion, so that a part of the air bubbles is exposed to the surface, and the surface of the concave portion becomes fine irregularities. Therefore, the foamed state of the foamed surface layer 244 has a correlation with the surface roughness of the above-described concave portion, and there is a tendency that the more the bubbles are present, the larger the surface roughness is.

A plurality of regions of the foamed surface layer 244 on the back surface 243 may be provided. When the area of the foamed surface layer 244 is a dot shape, the distribution thereof can be set, for example, to a random shape, a checkerboard shape, or a most densely packed shape. When the area of the foamed surface layer 244 is striped, its distribution can be set, for example, in a parallel stripe shape. Further, the region in which the foamed surface layer 244 is formed may also be the entire region of the back surface 243.

In addition, the light-emitting means of the light guide body 24 can be used in combination with the foamed surface layer 244 formed on the back surface 243 as described above by mixing the light-diffusing fine particles into the inside of the light guide body 24. Former. In addition, as the light guide body 24, in addition to the plate-shaped light guide body having the same thickness as shown in FIGS. 1 and 2 (the thickness of the concave surface of the foamed surface layer 244 of the back surface 243 is ignored), A light guide body having various cross-sectional shapes such as a wedge-shaped light guide body whose thickness gradually decreases from the light incident end surface 241 toward the opposite end surface can be used.

Further, a light-emitting mechanism including the foamed surface layer 244 as described above may be formed on the light-emitting surface 242, and a foamed surface layer including the above-described foamed surface layer may be formed on both of the light-emitting surface 242 and the back surface 243. 244 light exit mechanism.

The thickness of the light guide body 24 is, for example, 0.1 mm to 10 mm.

The light diffusing element 26 is disposed on the light emitting surface 242 of the light guiding body 24, and includes, for example, a light diffusing film. When the directivity of the light emitted from the light exit surface 242 has a desired exit angle and viewing angle, the light diffusing element 26 may be omitted.

The first optical deflecting element 28 is disposed on the light diffusing element 26, and the second optical deflecting element 30 is disposed on the first optical deflecting element 28. That is, the light diffusing element 26 is interposed between the first light deflecting element 28 and the light emitting surface 242 of the light guiding body.

The first light deflecting element 28 and the second light deflecting element 30 include a light incident surface that is closer to the light guide body 24 and a light emitting surface that is opposite to the light incident surface, and the light emitting surface includes a plurality of light emitting surfaces arranged in parallel with each other. Formed by a queue. However, the extending directions of the plurality of lines of the light-emitting surface of the first optical deflecting element 28 and the second optical deflecting element 30 are orthogonal to each other.

In the present embodiment, the extending direction of the plurality of rows of the light-emitting surface of the first optical deflecting element 28 is parallel to the light incident end surface 241, and the extending direction of the plurality of rows of the light-emitting surface of the second optical deflecting element 30 is The light incident end surface 241 is vertical. However, it is not limited to this. Both the extending direction of the plurality of rows of the light-emitting surface of the first light deflecting element 28 and the extending direction of the plurality of rows of the light-emitting surface of the second optical deflecting element 30 may be inclined with respect to the light incident end surface 241 and Orthogonal to each other.

The thickness of the first optical deflecting element 28 and the second optical deflecting element 30 is, for example, 30 μm to 350 μm.

When the light emitted from the light exit surface 242 has a peak in a desired direction, the first light deflecting element 28 or the second light deflecting element 30 may be omitted.

As the light reflecting element 32, for example, a plastic sheet having a metal vapor deposition reflective layer on its surface or a white sheet containing a pigment or a light-reflecting sheet such as a foam sheet can be used. Examples of the pigment include titanium oxide, barium sulfate, calcium carbonate, and magnesium carbonate. Further, it is preferable to add a reflection member to an end surface other than the end surface of the light incident end surface used as the light guide body 24. When the amount of light emitted from the back surface 243 is as small as negligible, the light reflecting element 32 may be omitted.

The light-emitting surface (second light) of the surface light source device including the LED 22, the light guide 24, the light diffusing element 26, the first light deflecting element 28, the second light deflecting element 30, and the light reflecting element 32 as described above A liquid crystal display element is disposed on the light-emitting surface of the deflecting element 30 to constitute a liquid crystal display device. The observer observes the liquid crystal display device through the liquid crystal display element from above in FIG.

In addition, the second light diffusing element can be disposed adjacent to the light-emitting surface of the second optical deflecting element 30, and glare or brightness unevenness which is a cause of deterioration in image display quality can be suppressed, and the quality of image display can be improved.

Next, an embodiment of the manufacturing method of the present invention for producing the light guide for a surface light source device as described above will be described.

First, a light guide material on which a foamed surface layer is not formed on the main surface is produced. The light guide material is a plate-shaped light guide material including an acrylic plate, and has the same thickness as the light guide 24 .

The light guide material is produced, for example, by a continuous plate making method (continuous casting method) in which a slurry of methyl methacrylate (syrup) is continuously injected into two rings which are disposed in a manner opposite to each other. The metal rotating belt was melted in a mold formed by sealing a gasket sandwiched between the belts at both side edges thereof to obtain a sheet.

Specifically, this method is a method for producing an acrylic plate-like polymer having a viscosity of 20 poise or more and polymerization at 20 ° C as disclosed in Japanese Laid-Open Patent Publication No. Hei 8-151403. One or more kinds of polymerization initiators are added to the methyl methacrylate-based slurry having a content of 25 wt% to 60 wt%, and the slurry is supplied to a mold and heated to 50 ° C to 100 ° C. Temperature to make the polymer content at least reach After 70% by weight, the polymerization is carried out by polymerization heat generation which is self-generated at a temperature substantially the same as or higher than the temperature of the slurry in the polymerization.

Here, it is preferred that the temperature is substantially the same as or higher than the temperature of the slurry in the polymerization, and is 60 ° C to 150 ° C. Further, it is preferred that the slurry having a polymerization by self-generated polymerization heat has a peak temperature of from 105 ° C to 140 ° C. Further, it is preferable that the mold is a two-layered belt which is disposed in the above-mentioned opposite manner and which moves at the same speed in the same direction, and a continuous mat which is moved by the endless belt at both side edges thereof. A mold made up of sheets.

The monomer which becomes a raw material of the slurry used in the present invention is a single methyl methacrylate or a monomer mixture containing methyl methacrylate as a main component, and when it is a monomer mixture, it is preferably a The methyl acrylate is 80% by weight or more.

Examples of the monomer used together with methyl methacrylate include ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, and 2-ethyl methacrylate. Ethyl ester such as ester, benzyl methacrylate, acrylate such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate or benzyl acrylate, styrene, α -methylstyrene and the like.

Examples of the polymerization initiator for polymerizing the above monomers to obtain a slurry include diisopropyl peroxydicarbonate, t-butyl peroxy neodecanoate, and peroxidation. Tert-butyl pivalate, third hexyl peroxypivalate, lauric acid peroxide, benzammonium peroxide, tert-butyl peroxydicarbonate, tert-butyl peroxybenzoate, An organic peroxide such as dicumyl oxide or di-tert-butyl peroxide; 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis(1-cyclohexanecarbonitrile), 2 An azo compound such as 2'-azobis(2,4,4-trimethylpentane). The addition amount of the polymerization initiator is usually 0.01% by weight to 0.5% by weight based on the monomer, but may be appropriately determined depending on the polymerization temperature or the target polymer conversion rate.

When a slurry is to be obtained, a molecular weight modifier can be used as needed. Specifically, a primary, secondary or tertiary thiol having an alkyl group or a substituted alkyl group such as n-butyl thiol, isobutyl thiol, n-octyl thiol, n-dodecyl sulphur may be mentioned. Alcohol, t-butyl mercaptan, second-dodecyl mercaptan, tert-butyl mercaptan, and the like. The amount of the molecular weight modifier to be used is not particularly limited, and for example, it can be preferably used in the range of 0.01% by weight to 0.2% by weight based on the slurry.

The slurry produced from the above monomer must be a slurry having a viscosity at 20 ° C of 100 poise or more and a polymer content of 25 wt % to 60 wt %. If the viscosity of the slurry is less than 100 poise or the polymer content is less than 25% by weight, the polymerization time becomes long. On the other hand, if the polymer content exceeds 60% by weight, it is difficult to mix the polymerization initiator or supply the slurry to the mold. material.

The slurry having the above-mentioned viscosity and the polymer content can be obtained by a known method, for example, in Japanese Patent Publication No. Sho 40-3701, Japanese Patent Publication No. Sho 47-35307, Japanese Patent Publication No. Sho 53-39918, and the like. The method described is manufactured.

Next, as the polymerization initiator added to the above slurry, the same polymerization initiator as that used in obtaining the above slurry was used. The amount of the polymerization initiator to be added is usually from 0.03 wt% to 0.5 wt%, based on the slurry.

Further, in the slurry used in the present invention, various additives such as an oxidation stabilizer, a plasticizer, a dye, a pigment, a release agent and the like may be further added as needed.

The mold for obtaining the acrylic plate-like polymer of the present invention is preferably as described above in Japanese Patent Publication No. Sho 46-41602, Japanese Patent Publication No. Sho 47-33495, and the like. Two annular belts arranged in the same direction and moving at the same speed in the same direction, and continuous slab-shaped polymers composed of continuous gaskets sandwiched by the endless belts on both side edges thereof The mold of the way.

FIG. 5 is a schematic explanatory view showing an example of a polymerization apparatus for continuously producing the acrylic plate-like polymer (light guide material) of the present invention.

In the polymerization apparatus shown in Fig. 5, two stainless steel endless belts 1, 1' arranged vertically are respectively provided with tension by the main pulleys 2, 3, 2', 3', and are identical in the same direction. The way the speed moves is driven.

The roller 4 horizontally supports the moving endless belt and defines the distance between the belt faces, i.e., the thickness of the slurry.

The slurry is sent from the storage tank to the slurry supply pipe 5 by a metering pump or the like (not shown), and is supplied to the endless belt 1'.

Both side edges between the belt faces are sealed by a continuous elastic gasket 6 and are moved by the endless belts 1, 1'.

The slurry supplied to the endless belt 1' is held by the endless belts 1, 1', and is sequentially passed through the heating zones 15, 16, 17, and 18 to complete the polymerization, thereby forming the plate-like polymer 19.

In Fig. 5, it is shown that the heating zone 15 is heated by air by the vapor line 7, and the heating zones 16, 17 are used by the blowers 11, 12, 13. The hot air is heated, and the heating zone 18 is heated by the air of the vapor line 8, and the drain lines 9, 10 are for discharging the drains occurring in the heating zones 15, 18, and the heat exchanger 14, 14' is to adjust the temperature of the hot air. However, other heating methods such as water bath heating, electrothermal heating, infrared heating, electromagnetic induction heating, and the like can be used. In the present invention, methods such as hot air heating, electrothermal heating, and infrared heating are preferably used.

The process of the present invention is carried out as described above using a polymerization apparatus, but the slurry is preheated to between 50 ° C and 90 ° C in the heating zone 15 .

The slurry is polymerized in the heating zones 16, 17 and polymerized to a polymer content of at least 70% by weight, preferably 70% by weight to 90% by weight. In the heating zones 16, 17, the polymerization temperature of the slurry is maintained in the range of 60 °C to 100 °C. Further, the polymer content shown here is obtained by taking out a sample in the middle of a batch plate making test and rapidly cooling it, thereby stopping the polymerization and measuring it.

Then, in the heating zone 18, the slurry is further polymerized to complete the polymerization, and the heating zone 18 is maintained at a temperature substantially equal to or higher than the temperature of the slurry during the polymerization, preferably 60 ° C to 150 ° C. The polymerization is carried out by polymerization heating of the self-generated slurry. That is, the polymerization is actively used to complete the polymerization. The polymerization peak temperature of the slurry at this time is from 105 ° C to 140 ° C, preferably from 110 ° C to 130 ° C.

In the method of the present invention, when the polymer content is less than 70% by weight and is polymerized by polymerization heat generated at a temperature substantially the same as or higher than the temperature of the slurry in the polymerization, the plate-like polymer is produced. Bubbles, so it is not good.

The substantial completion of the polymerization is achieved by making the polymer content at least 95 wt%, preferably 95 wt% or more is achieved.

Then, the main surface of the light guide material obtained in the above manner is subjected to etching (laser etching) by laser light irradiation to form a foamed surface layer 244 on the surface layer portion of the main surface of the light guide material.

As the laser for laser etching, it is preferable to use a laser having a good etching efficiency for a light guide material, for example, an infrared laser such as a carbon dioxide laser (CO ₂ laser). As the carbon dioxide laser, a CO ₂ laser marking machine manufactured by KEYENCE Corporation (ML-Z9520T: an oscillation wavelength of 9.3 μm and an average output of 20 W) can be cited.

As described above, the longitudinal section shape (contour of the foamed surface layer 244 can be easily made by changing the distance of the laser output, the scanning speed, and the focus position (focus position) of the main surface of the light guide material. )Variety.

6 and FIG. 7 are diagrams each showing a comparison with FIG. 3 and FIG. 4 of the present invention, and are laser-etched portions of the light guide material including the acrylic resin sheet obtained by extrusion molding. SEM top view and SEM section perspective view. In this case, a foamed surface layer was not formed. When an acrylic resin sheet produced by an extrusion molding method is used as a light guide material, the molecular weight of the polymer is lower than that of the above-described present invention, and therefore it is presumed that it is not the same as the present invention in laser etching. Processing mechanism.

[Example]

Hereinafter, the present invention will be more specifically described by way of examples and comparative examples.

(Example 1)

<Production of Light Guide Material>

Using the device shown in Figure 5, according to the Japanese patent special Kaiping In Example 1 of No. 8-151403, a light guide material was produced as follows.

Using a pump at a flow rate of 6 kg/h, it will contain 0.016 wt% of 2,2'-azobis(2,4-dimethylvaleronitrile), 0.2 wt% of n-dodecylmercaptan, and 4 wt% of butyl acrylate. The ester methyl methacrylate was supplied to the polymerization tank, and the internal liquid of the polymerization tank was sufficiently and uniformly stirred, and then the temperature was maintained at 130 ° C and polymerization was carried out for 10 minutes. The polymer content (slurry) on the discharge side had a polymer content of 28% by weight and a viscosity of 12 poise.

The slurry was cooled by a condenser, and fed by a gear pump at a flow rate of 4.5 kg/h, and then a polymer content of 20 wt% was added thereto by a pump at a ratio of 0.5 kg/h, and contained 0.32 wt%. A polymerization initiator of peroxidic pivalic acid trihexyl ester and 0.008% by weight of azobisisobutyronitrile maintained at 10 ° C in a slurry of methyl methacrylate and mixed by a static stirrer built therein Machine mix.

Then, the slurry was supplied to the slurry tube at a flow rate of 0.83 kg/h to a thickness of 1.5 mm, a width of 500 mm, a length of 10 m (annular band 1), and a length of 12 m (annular band 1'). It is composed of two stainless steels, and is moved over the endless belt 1' of 0.04 m per minute, and is rolled by the upper and lower endless belts 1, 1'. Further, the gasket 6 is a hollow tube made of soft vinyl chloride. In the heating zone 15, the slurry rolled by the belt was heated to 70 ° C, and then left in the heating zone 16 (hot air 82 ° C) for 4 minutes and in the heating zone 17 (hot air 69 ° C) for 9 minutes. The heating zone was sequentially passed through the heating zone 18 (100 ° C) for 6 minutes to obtain a transparent acrylic cast plate having a thickness of 0.5 mm.

The acrylic cast plate was cut into a rectangle having a width of 30 mm and a length of 100 mm to obtain a light guide material A1.

<Production of Light Guide for Surface Light Source Device>

A schematic view of the sample (light guide B1 for a surface light source device) produced in the present example is shown in Figs. 8a and 8b. Fig. 8a shows a plan view and Fig. 8b shows a longitudinal section. Referring to Fig. 8a and Fig. 8b, a processing procedure for obtaining the light guide B1 for the surface light source device from the light guide material A1, in particular, a laser etching process will be described. In addition, for convenience of explanation, each part of the light guide material is referred to by the same name as the portion corresponding to the light guide. The same is true below.

Using CO ₂ laser marking machine ML-Z9520T (wavelength: 9.3 μm, average output: 20 W) manufactured by KEYENCE, the output is 80%, the scanning speed is 500 mm/sec, and the laser focus position and processing surface Under the condition of the coincidence, the surface of the light guide material A1 facing the light exit surface 110 (the back surface opposite to the light exit surface 110) 130 is subjected to laser etching processing, and a concave foamed surface layer is provided as a unit point. A plurality of recesses (light emitting means) 101 formed by the unit dots are arranged to obtain a light guide B1 for the surface light source device. The laser etched pattern is set to a dot shape, and the light incident end surface 120 is 50 mm, and the side end surface is 15 mm as the center of the 6 mm × 6 mm region, and the light incident end surface 13 patterns arranged in a parallel direction of 120 are arranged at a pitch of 0.5 mm, and 13 patterns are arranged at a pitch of 0.5 mm in a direction corresponding to the light guiding direction of the light guiding body (a direction parallel to the side end faces).

<Observation and measurement of foamed surface layer>

The surface of the concave foamed surface layer of the light guide B1 for the surface light source device obtained was observed by a scanning electron microscope (SEM, S-4300SE/N scanning electron microscope manufactured by Hitachi High Technologies Co., Ltd.). Shape and profile shape. Observing the arbitrarily selected unit point, and from the surface of the light guide body (the surface of the unit point) to the deepest point of the bubble located in the thickness direction of the light guide body, within the range observed The length in the thickness direction up to the portion is set to "the thickness of the foamed surface layer". Further, the length of the bubble in the foamed surface layer in the thickness direction was measured, and the maximum value thereof was set to "the diameter of the bubble".

<Measurement of Surface Roughness of Foamed Surface Layer>

The concave foaming surface layer of the light guide B1 for the surface light source device obtained was obtained by using a laser conjugated focus microscope (scanning conjugated focal laser microscope LEXT OLS-3000 manufactured by Olympus) Surface roughness (arithmetic mean roughness: Ra) was evaluated. The three-dimensional contour of the concave foamed surface layer was measured by the above laser conjugate focal length microscope, and based on the obtained profile, the surface roughness curve was selected using the analysis software LEXT OLS application program (version 5.0.7), and Ra was calculated. . The cutoff value was set to λc=1/10, and the above-described measurement was performed on the points of the three portions that were arbitrarily selected, and the average value of the total of nine data obtained by measuring the three portions in each point was taken as the Ra value. .

<Optical evaluation>

(1) Evaluation of brightness distribution

9 is a schematic diagram of an assay system for luminance distribution evaluation. The luminance distribution of the surface light source device using the light guide B1 for the surface light source device was evaluated by the following method.

The LED light source 340 (LED NSSW020BT 1 lamp manufactured by Nichia Chemical Co., Ltd.) which emits light at 20 mA by the constant current power source 350 is disposed on the light incident end surface 302 of the light guide B1 for the surface light source device for measurement, and reflects Sheet 310 (manufactured by DuPont Film Co., Ltd. having a UX thickness of 225 μm) was disposed on the back side 303 on the opposite side of the light exit surface. Using the luminance meter 360 (luminance meter BM-7 manufactured by TOPCON Co., Ltd.), the light emitted from the light exit surface 304 of the region having the center of view of the portion where the foamed surface layer (light emitting mechanism) 301 is provided as the center is measured. The luminance distribution at an outgoing light angle from -90 degrees to 90 degrees in a plane parallel to the light guiding direction and perpendicular to the light guiding light exit surface 304. Further, the emission direction is set to 0 degree in the normal direction, the direction in which the light incident surface 302 is observed from the foamed surface layer (light emitting means) 301 is set to - (negative), and the opposite direction is set to + (positive). . Based on the measurement result, a half value angle range (degrees) of the luminance distribution is obtained. The results of the evaluation will be described later.

(2) Evaluation of luminous quality

Fig. 10 is a schematic diagram of an evaluation system for illuminating quality observation. The light-emitting quality of the surface light source device using the light guide B1 for the surface light source device was evaluated by the following method.

The LED light source 340 (LED NSSW020BT 1 lamp manufactured by Nichia Chemical Co., Ltd.) which emits light at 20 mA by the constant current power source 350 is disposed on the light incident end surface 302 of the light guide B1 for the surface light source device for measurement, and reflects Sheet 310 (manufactured by DuPont Film Co., Ltd. having a UX thickness of 225 μm) was disposed on the back side 303 on the opposite side of the light exit surface. The diffusion sheet 220 as a light diffusion element and the cymbals 230 and 240 as the first and second optical deflection elements are disposed adjacent to the light guide light emitting surface 304. The cymbal sheet is disposed in a direction in which the yoke formation surface faces the light emission surface 304 of the surface light source device light guide B1 on the opposite side (upward). In other words, the cymbals 230 and 240 are provided with a light-incident surface on the side closer to the light guide B1 for the surface light source device and a light-emitting surface on the opposite side to the light-incident surface, and the light-emitting surface is formed by including a plurality of arrays. As the diffusion sheet 220, a high-intensity diffusion film Light-Up 100GM3 for a liquid crystal display (LCD) backlight manufactured by KIMOTO Co., Ltd. was used as the ruthenium sheets 230 and 240, and a brightness rising film Vikuiti BEFII90/ manufactured by Sumitomo 3M Co., Ltd. was used. 50. The first cymbal 230 is disposed such that the louver and the light guide light incident end surface 302 are parallel to each other, and the second cymbal 240 is such that the light guide directions of the array and the light guide are parallel to each other (ie, 稜鏡The column and the light guide light incident end surface 302 are perpendicular to each other.

In the same manner as the luminance distribution evaluation described above, the LED 340 is caused to emit light, and it is visually confirmed whether or not the laser spot pattern can be recognized, thereby evaluating the light-emitting quality, and setting the point formed by the laser etching to "x". The point formed by the laser etching cannot be recognized, and the illuminator as the surface can be set to "○". The results of the evaluation will be described later.

(Example 2)

An acrylic cast plate (ACRYLITE LX001 manufactured by Mitsubishi Rayon Co., Ltd.) having a thickness of 0.5 mm was cut into a rectangle having a width of 30 mm and a length of 100 mm to obtain a light guide material A2. The light guide body B2 for a surface light source device was produced in the same manner as in Example 1 using the light guide material A2. With respect to the obtained light guide B2 for a surface light source device, observation of the concave foamed surface layer, measurement of surface roughness, and optical evaluation were performed in the same manner as in Example 1. The result will be described later.

(Example 3)

Fig. 11 is a schematic configuration view showing an apparatus for continuously manufacturing a plate-shaped light guide material in the present example. In this apparatus, an ultraviolet polymerizable viscous liquid (slurry) 402 is supplied from the supply die 401 to produce an acrylic cast plate (light guide material) 402'. The first film 413 is moved by the feeding device 414 and the winding device 415, and the second film 416 is moved by the feeding device 417 and the winding device 418. The supplied ultraviolet ray-polymerizable viscous liquid 2 is sandwiched between the first film 413 and the second film 416, and is pressed by the upper surface pressing roller 408 and the lower surface pressing roller 408' to have a layer thickness of a desired thickness. And move. In the meantime, the ultraviolet ray irradiation device 404 is irradiated with ultraviolet rays through the first film 413 and the second film 416, and further heated by the hot air heating device 410 to polymerize the ultraviolet ray-polymerizable viscous liquid 402 to become the acrylic cast plate 402. '.

In the present example, first, a UV-decomposition polymerization initiator 1-hydroxy-cyclohexyl-phenyl ketone (Irgacure 184 manufactured by Ciba Speciality Chemicals Co., Ltd.) was added to 60 parts by weight of a methyl methacrylate monomer. 0.05 part by weight of n-octyl mercaptan and 0.1 part by weight of sodium dioctylsulfosuccinate (Aerosol OT-100 manufactured by Mitsui-Cyanamid Co., Ltd.) as a release agent, and dissolved at room temperature, at 80 parts by weight 40 parts by weight of methyl methacrylate polymer beads (BR-80 weight average molecular weight of 100,000 manufactured by Mitsubishi Rayon Co., Ltd.) was heated and dissolved at a temperature of 30 ° C to prepare a UV-polymerizable viscous liquid 402. In order to remove the bubbles at the time of mixing, it was allowed to stand at 50 ° C for 2 hours, and then naturally cooled to normal temperature.

Then, the above-mentioned ultraviolet polymerizable viscous liquid 402 was used, and an acrylic cast plate 402' was produced by the apparatus shown in FIG. As the first film 413 and the second film 416, a polyethylene terephthalate film (Cosmoshine A4100 manufactured by Toyobo Co., Ltd.) having a width of 500 mm and a thickness of 188 μm was used as the ultraviolet irradiation device 404, and Toshiba was used. The company's FL30S-BL lamp.

The transport speed of the first film 413 and the second film 416 was set to 0.13 m/min, and the previously prepared ultraviolet polymerizable viscous liquid 402 was supplied from a supply die 401 in a sheet shape having a width of 400 mm and a thickness of 0.58 mm. After the film 416 is applied, the film 413 is covered with the ultraviolet ray-polymerizable viscous liquid 402. Thereafter, the ultraviolet ray irradiation device 404 irradiates the ultraviolet ray at an irradiation intensity of 2 mW/cm ² for 20 minutes, and after heat treatment at 143 ° C for 3 minutes by the hot air heating device 410, the air is cooled to 90 ° C, and then from the first film 413 and The second film 416 was peeled off, whereby an acrylic cast plate 402' having a thickness of 0.5 mm was obtained. The obtained acrylic cast sheet 402' was cut into a rectangle having a width of 30 mm and a length of 100 mm, whereby the light guide material A3 was produced.

The light guide body B3 for a surface light source device was produced in the same manner as in Example 1 using the obtained light guide material A3. The observation of the concave foamed surface layer, the measurement of the surface roughness, and the optical evaluation were carried out in the same manner as in Example 1 with respect to the light guide B3 for the surface light source device. The result will be described later.

(Comparative Example 1)

The light guide material A4 was produced in the same manner as in Example 3 except that the amount of the n-octyl mercaptan added in the preparation of the ultraviolet-polymerizable viscous liquid 402 was 0.135 parts by weight.

Using the obtained light guide material A4, a light guide B4 for a surface light source device was produced in the same manner as in Example 1. In the same manner as in Example 1, the light guide B4 for the surface light source device was subjected to concave observation, surface roughness measurement, and optical evaluation. The result will be described later.

(Comparative Example 2)

An acrylic resin pellet (Acrypet VH000 manufactured by Mitsubishi Rayon Co., Ltd.) was used as a raw material, and an acrylic extrusion plate having a thickness of 0.5 mm obtained by a known extrusion process was cut into a width of 30 mm and a length of 100 mm. The rectangle is made to form the light guide material A5.

Using the obtained light guide material A5, a light guide B5 for a surface light source device was produced in the same manner as in Example 1. In the same manner as in Example 1, the light guide B5 for the surface light source device was subjected to concave observation, surface roughness measurement, and optical evaluation. The result will be described later.

(Comparative Example 3)

The light guide B1 for the surface light source device produced in Example 1 was used as a master mold, and a mold obtained by transferring the surface shape of the laser spot portion by using ruthenium rubber (TEE3450 manufactured by Momentive Performance Materials Co., Ltd.) was used. The ultraviolet curable monomer mixture having a refractive index of 1.51 after hardening was developed on the surface of the mold, and the light guide material A1 used in Example 1 was laminated thereon, and then irradiated from the side of the light guide material A1. In the ultraviolet light, the light guide device B6 for the surface light source device in which the surface shape of the light-emitting mechanism portion of the light guide device B1 for the surface light source device is reproduced by transfer is produced.

With respect to the obtained light guide B6 for a surface light source device, concave observation, surface roughness measurement, and optical evaluation were performed in the same manner as in Example 1. The result will be described later.

[Evaluation Results of Examples 1 to 3 and Comparative Examples 1 to 3]

The observation results (SEM photographs) of the surface and cross section of the concave portion of the light guides (B1 to B6) for the surface light source device produced in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Fig. 12 .

As shown in FIG. 12, the concave light of the main surface of the light guide B1 for the surface light source device B1 to the light guide B3 for the surface light source device produced in Examples 1 to 3 is formed by laser etching. In the mechanism portion, irregularities of several μm order were observed on the surface, and it was found that a plurality of bubbles were partially present in the vicinity of the inclined surface in the cross section. In other words, the foamed surface layer is a layer having a fine structure having a crack-generating shape, a depressed pore shape, or a void-encapsulated shape, and is a layer containing bubbles in the above-described fine structure.

On the other hand, fine irregularities were observed on the surface of the concave portion of the light guide B4 for the surface light source device produced in Comparative Example 1, but no bubbles were observed in the cross section, and it was found that only the unevenness of the surface was observed. A foamed surface layer is formed. In addition, the surface of the concave portion of the light guide B5 for the surface light source device produced in Comparative Example 2 was smooth, and no bubbles were observed in the cross section, and it was found that the foamed surface layer was not formed. Further, the light guide B6 for a surface light source device produced in Comparative Example 3 has the shape of the light guide B1 for the surface light source device produced in Example 1 by transfer, so the concave portion has the same surface as B1, but There were no bubbles in the cross section, and it was found that only the unevenness of the surface was formed, and the foamed surface layer was not formed.

FIG. 13 is a view showing the distribution of the luminances of the respective exit angles of the light guide bodies of the light guides (B1 to B6) for the surface light source device produced in the examples 1 to 3 and the comparative examples 1 to 3. The graph of the luminance distribution measured by the measurement method of FIG. 9 is a material for normalizing the value of the peak luminance to 1.0 in order to compare the contour of the luminance distribution. In addition, in the figure, the horizontal axis represents the angle (exit angle) of the emitted light, the vertical axis represents the relative brightness at the angle, and the exit angle is - (negative) the direction in which the light incident end face is observed from the light exiting mechanism, to + (Positive) to indicate the opposite direction.

Table 1 is obtained by observing the thickness of the foamed surface layer and the diameter of the bubble obtained from the results of the cross-sectional observation, the arithmetic mean roughness (Ra) obtained from the result of the surface roughness measurement, and the result of evaluation based on the luminance distribution. A table summarizing the results of the half value angle range and the illuminance quality evaluation. Here, the half value angle range refers to an angle range in which a value of 50% (relative brightness = 0.5) or more of the peak value in each of the emission profiles of FIG. 13 is taken.

As shown in Table 1, the light guide for a surface light source device of Examples 1 to 3 having a foamed surface layer on the surface of a concave portion provided by laser etching has a wide range of a half value angle range of 80 degrees or more. The luminance distribution characteristics, particularly the luminance in the normal direction (the 0 degree direction in Fig. 13), become high. Therefore, when the surface light source device is configured in combination with the optical element, it is possible to obtain light emission in which the laser spot is not easily recognized and has high quality.

On the other hand, the light guides for the surface light source device of Comparative Example 1 and Comparative Example 2 which do not have the foamed surface layer respectively exhibit luminance distribution characteristics having a half value angle range of 64 degrees and 42 degrees, and the luminance distribution characteristics and examples In the case of the light guide for the surface light source device of the first to third embodiments, the light-emitting device has a narrow emission pattern with high directivity. Therefore, when the surface light source device is configured in combination with the optical element as in the case of the light guide for the surface light source device of Examples 1 to 3, the laser spot is easily recognized. In order to improve the penetration phenomenon at this point and obtain a higher illuminating quality, it is necessary to form a laser spot at a finer and higher density, and as a result, laser etching takes a long time and causes a decrease in productivity. Further, since the light guide B6 for the surface light source device of Comparative Example 3 has a surface shape transferred from B1, it has the same surface roughness as B1, but does not have a foamed surface layer. Therefore, only the scattering effect by the unevenness of the surface is obtained, and a high scattering effect caused by the difference in refractive index from the gas contained in the bubble cannot be obtained. Therefore, compared with the example 1, the half value angle range is significantly narrowed, and the laser spot is easily recognized.

(Example 4)

The amount of the ultraviolet-decomposable polymerization initiator 1-hydroxy-cyclohexyl-phenyl ketone when the ultraviolet ray-polymerizable viscous liquid 402 was prepared was set to 0.05 parts by weight, and the amount of n-octyl thiol added was set to 0.05 weight. A light guide material A7 was produced in the same manner as in Example 3 except for the parts.

Using the obtained light guide material A7, the conditions at the time of laser etching processing were set to be 80%, the scanning speed was 500 mm/sec, and the laser focus position was from the processing surface (back surface 130) toward the laser light source. A light guide B7 for a surface light source device was produced in the same manner as in Example 1 except that the side was shifted by 10 mm. The observation of the concave foamed surface layer, the measurement of the surface roughness, and the optical evaluation were carried out in the same manner as in Example 1 with respect to the light guide B7 for the surface light source device. However, in the evaluation of the light-emitting quality, the diffusion sheet and the cymbal sheet (two sheets) were placed adjacent to the light-guide body light-emitting surface 304 in the same manner as in the example 1, and the diffusion sheet used in the first example 1 was further disposed (KIMOTO). The LCD backlight manufactured by the company was evaluated with a high-brightness diffusion film Light-Up 100GM3). The result will be described later.

(Comparative Example 4)

A light guide device B8 for a surface light source device was produced in the same manner as in Example 4 except that the light guide material A5 used in Comparative Example 2 was used as the light guide material. In the same manner as in Example 4, the light guide B8 for the surface light source device was subjected to concave observation, surface roughness measurement, and optical evaluation. The result will be described later.

[Evaluation Results of Example 4 and Comparative Example 4]

The observation results (SEM photographs) of the surface and the cross section of the concave portion of the light guides (B7 to B8) for the surface light source device produced in Example 4 and Comparative Example 4 are shown in Fig. 14 .

As shown in FIG. 14 , a concave light-emitting mechanism portion formed on the main surface of the light guide B7 for a surface light source device produced in Example 4 by laser etching was observed on the surface in the order of several μm. Concavities and convexities, and it is known that a plurality of bubbles are partially present in the vicinity of the inclined surface. On the other hand, the surface of the light-emitting mechanism portion of the light guide B8 for a surface light source device produced in Comparative Example 4 was smooth, and bubbles were not observed in the cross section, and it was found that the foamed surface layer was not formed.

15 is a graph showing the luminance distribution of each of the light guides of the light guides (B7 to B8) for the surface light source device produced in Example 4 and Comparative Example 4, in order to compare the luminance distributions. The outline indicates data that is normalized by setting the value of the peak luminance to 1.0. In addition, in the figure, the horizontal axis represents the angle (exit angle) of the emitted light, the vertical axis represents the relative brightness at the angle, and the exit angle is - (negative) the direction in which the light incident end face is observed from the light exiting mechanism, to + (Positive) to indicate the opposite direction.

Table 2 is the arithmetic mean roughness (Ra) obtained by the thickness of the foamed surface layer and the diameter of the bubble obtained from the results of the cross-sectional observation, and the results obtained from the results of the surface roughness measurement, and the results obtained from the evaluation of the luminance distribution A table summarizing the results of the half value angle range and the illuminance quality evaluation. Here, the half value angle range means an angle range in which the value of 50% (relative brightness = 0.5) or more of the peak value in each of the emission profiles of FIG. 15 is taken.

As shown in Table 2, the light guide for a surface light source device of Example 4 having a foamed surface layer on the surface of the concave portion provided by laser etching has a wide luminance distribution characteristic having a half value angle range of 60 degrees, in particular The brightness in the normal direction becomes high. Therefore, when the surface light source device is configured in combination with the optical element, it is possible to obtain light emission in which the laser spot is not easily recognized and has high quality.

On the other hand, the light guide for the surface light source device of Comparative Example 4 which does not have the foamed surface layer exhibits a luminance distribution characteristic having a half-value angular range of 38 degrees, and the luminance distribution characteristic is the light guide for the surface light source device of Example 4. Compared with the case of the body, it becomes a narrow and highly directional exit pattern. Therefore, when the surface light source device is configured in combination with the optical element as in the case of the light guide for the surface light source device of Example 4, the laser spot is easily recognized. In this case, in order to improve the point penetration phenomenon, a higher illuminating quality is obtained, and it is necessary to form a laser spot at a finer and higher density, so as a result, laser etching takes a long time, and Causes a decline in productivity.

(Example 5)

<Production of Light Guide for Surface Light Source Device>

The acrylic cast sheet produced in the same manner as in Example 1 was cut into a rectangle having a width of 100 mm and a length of 100 mm to prepare a light guide material A9.

A schematic diagram of a sample (light guide device B9 for a surface light source device) produced using the obtained light guide material A9 in the present example is shown in Figs. 16a and 16b. Fig. 16a shows a plan view and Fig. 16b shows a longitudinal section. Referring to Fig. 16a and Fig. 16b, a processing procedure for obtaining the light guide B9 for the surface light source device from the light guide material A9, in particular, a laser etching process will be described.

KEYENCE Corporation CO _{2 is} used at a position in the width direction (vertical direction in the vertical direction of FIG. 16a) of the back surface 130 of the light guide material material A9 opposite to the light exit surface 110 from the light incident end surface 120 of 50 mm. Laser marking machine ML-Z9520T (wavelength: 9.3 μm, average output: 20 W), set the laser output to 90%, set the scanning speed to 75 mm/sec, and position the laser focus from the processing surface ( The back surface 130) is subjected to laser etching under the condition that the laser light source side is shifted by 9 mm, and a concave portion 101 which is a V-groove longitudinal section of the light-emitting means is formed. The pattern of the laser etching was set to a stripe shape parallel to the light incident end surface 120, and the length was set to 10 mm.

Thereby, the light guide B9 for a surface light source device is obtained. The surface layer portion of the concave portion 101 serves as the foamed surface layer 244.

The shape, width, depth, and inclination of the light incident end surface side of the concave portion 101 and the foamed surface layer 244 in the light guide B9 for the surface light source device obtained by an optical microscope (IC inspection microscope ECLIPSE L200N manufactured by Nikon Corporation) The angle (inclination angle on the incident surface side) α was evaluated. The result is shown in Fig. 18.

Further, in the same manner as in Example 1, the surface of the inclined surface of the concave portion 101 and the foamed surface layer 244 on the light incident end surface side and the cross-sectional shape were observed by SEM. The result will be described later.

<Optical evaluation>

The surface light source device was fabricated using the above-described surface light source device with the light guide B9, and the optical characteristics thereof were evaluated. Figure 17 shows what it looks like.

Five LEDs 340 (LED NSSW020BT manufactured by Nichia Corporation) are arranged at equal intervals adjacent to the light incident end surface 302 of the light guide B9 for the surface light source device. A reflection sheet 310 (Lumirror E20 manufactured by Toray Industries, Inc.) as a light reflection element is disposed adjacent to the back surface 303 of the light guide B9 for the surface light source device and separated by an air layer.

The LED 340 is made to emit light at 20 mA by the constant current power source 350, and the brightness angle meter 360 (luminance meter BM-7 manufactured by TOPCON Co., Ltd.) is used, and the angle of view from the portion where the foamed surface layer (light emitting mechanism) 301 is centered is measured. The luminance distribution of the light emitted from the light exit surface 304 of the region of 2 degrees from the exit light angle of -90 degrees to 90 degrees of the surface parallel to the light guiding direction and perpendicular to the light exit surface 304. Further, regarding the angle of the outgoing light, the normal direction of the light exit surface is set to 0 degrees, the direction in which the light incident end surface 302 is observed from the foamed surface layer 301 is set to - (negative), and the opposite direction is set to + (positive). ). The measurement results are shown in Fig. 20 .

Then, the cymbals 230 and 240 which are the first and second optical deflecting elements which are disposed adjacent to the light guide light emitting surface 304 are disposed on the side of the matrix forming surface and the light of the light guide B9 for the surface light source device. Face 304 is in the opposite side (upward) direction. In other words, the cymbals 230 and 240 include a light incident surface on the side closer to the light guide B9 for the off-surface light source device, and a light exit surface on the opposite side to the light incident surface, and the light exit surface is formed by including a plurality of arrays. As the cymbals 230 and 240, a brightness rising film Vikuiti BEFII 90/50 manufactured by Sumitomo 3M Co., Ltd. was used. The first cymbal 230 is disposed such that the louver and the light guide light incident end surface 302 are parallel to each other, and the second cymbal 240 is disposed such that the light guiding directions arranged in the matrix and the light guide are parallel to each other (ie, 稜鏡The column is in a direction perpendicular to the light incident end face 302 of the light guide.

The LED 340 was caused to emit light in the same manner as described above, and the luminance distribution at the light emission angle was measured using a luminance meter 360 (luminance meter BM-7 manufactured by TOPCON Co., Ltd.). The measurement results are shown in Fig. 21 .

(Comparative Example 5)

An acrylic resin pellet (Acrypet VH000 manufactured by Mitsubishi Rayon Co., Ltd.) was used as a raw material, and an acrylic extrusion plate having a thickness of 0.5 mm obtained by a known extrusion process was cut into a width of 100 mm and a length of 100 mm. The light guide body B10 for the surface light source device was produced in the same manner as in Example 5, using the obtained rectangle as the light guide material.

With respect to the obtained light guide B10 for a surface light source device, the shape, the width, the depth, and the inclination angle (incidence angle on the incident surface side) α of the concave portion 101 were evaluated in the same manner as in Example 5. The result is shown in Fig. 18.

Further, in the same manner as in Example 5, the surface of the inclined surface of the concave portion 101 on the light incident end surface side and the form of the cross section were observed. The result will be described later.

Further, using the light guide B10 for a surface light source device described above, a surface light source device was produced in the same manner as in Example 5, and the luminance distribution at the light emission angle was measured. The measurement results are shown in Fig. 20 and Fig. 21 .

(Example 6)

Laser etching was performed at a laser output of 90%, a scanning speed of 75 mm/sec, and a laser focus position shifted by 7 mm from the processing surface toward the laser source side, in addition to Example 5 The light guide B11 for the surface light source device was produced in the same manner.

The shape, width, depth, and inclination angle of the light incident end surface side of the concave portion 101 and the foamed surface layer 244 (inclination angle of the incident surface side) were evaluated in the same manner as in Example 5 with respect to the light guide B11 for the surface light source device obtained. ) α. The result is shown in Fig. 18.

Further, in the same manner as in Example 5, the surface of the inclined surface of the concave portion 101 and the foamed surface layer 244 on the light incident end surface side and the form of the cross section were observed. The result will be described later.

Further, a surface light source device was produced in the same manner as in Example 5 using the light guide B11 for a surface light source device, and the luminance distribution at the light emission angle was measured. However, the cymbal 240 is not used. The measurement results are shown in Fig. 22 and Fig. 23.

(Comparative Example 6)

A light guide body B12 for a surface light source device was produced in the same manner as in Example 6 except that the acryl extruded sheet used in Comparative Example 5 was used as the light guide material.

With respect to the obtained light guide B12 for a surface light source device, the shape, the width, the depth, and the inclination angle (inclination angle on the incident surface side) α of the concave portion 101 were evaluated in the same manner as in Example 5. The result is shown in Fig. 18.

Further, in the same manner as in Example 5, the surface of the inclined surface of the concave portion 101 on the light incident end surface side and the form of the cross section were observed. The result will be described later.

Further, a surface light source device was produced in the same manner as in Example 6 using the light guide B12 for a surface light source device described above, and the luminance distribution at the light emission angle was measured. The measurement results are shown in Fig. 22 and Fig. 23.

(Example 7)

Laser etching was performed at a laser output of 70%, a scanning speed of 75 mm/sec, and a laser focus position shifted from the machined surface to the side of the laser source by 2 mm, in addition to Example 5 The light guide B13 for the surface light source device was produced in the same manner.

The shape, the width, the depth, and the inclination angle of the light incident end face side (inclination angle of the incident surface side) of the concave portion 101 and the foamed surface layer 244 were evaluated in the same manner as in Example 5 with respect to the light guide B13 for the surface light source device obtained. ) α. The result is shown in Fig. 18.

Further, in the same manner as in Example 5, the surface of the inclined surface of the concave portion 101 and the foamed surface layer 244 on the light incident end surface side and the form of the cross section were observed. The result will be described later.

Further, a surface light source device was produced in the same manner as in Example 5 using the light guide B13 for a surface light source device, and the luminance distribution at the light emission angle was measured. However, the cymbals 230, 240 are not used. The measurement results are shown in Fig. 24 .

(Comparative Example 7)

A light guide B14 for a surface light source device was produced in the same manner as in Example 7 except that the acrylic extruded sheet used in Comparative Example 5 was used as the light guide material.

With respect to the obtained light guide B14 for a surface light source device, the shape, the width, the depth, and the inclination angle (incidence angle on the incident surface side) α of the concave portion 101 were evaluated in the same manner as in Example 5. The result is shown in Fig. 18.

Further, in the same manner as in Example 5, the surface of the inclined surface of the concave portion 101 on the light incident end surface side and the form of the cross section were observed. The result will be described later.

Further, a surface light source device was produced in the same manner as in Example 7 using the light guide B14 for a surface light source device described above, and the luminance distribution at the light emission angle was measured. The measurement results are shown in Fig. 24 .

[Examples 5 to 7 and Comparative Examples 5 to 7]

The "shape" in the above-mentioned FIG. 18 is the V-groove cross section of the light-emitting means for constituting the light guides (B9 to B14) for the surface light source device produced in the examples 5 to 7 and the comparative examples 5 to 7. The result of observation of the cross section of the concave portion 101 and the foamed surface layer 244. The inclined surface on the left side in the figure corresponds to the light incident end surface side.

As shown in FIG. 18, it is understood that a V-groove shape in which the angle of the inclined surface is controlled to a specific angle can be formed by appropriately adjusting the conditions of the laser output, the scanning speed, and the focus position at the time of laser etching. In addition, it is understood that the light guide body produced using any of the light guide material including the acrylic cast plate and the light guide material including the acrylic extruded plate is formed to have substantially the same inclination angle. Light exit mechanism unit.

19a to 19d are views showing SEM observation results of the inclined surface on the light incident end surface side of the light-emitting mechanism portion. Here, as a representative shape, the light guide samples B11 and B12 obtained in Example 6 and Comparative Example 6 indicate the inclined surface (Fig. 19a, Fig. 19c) and the inclined surface (Fig. 19b, Fig. 19d). ) observations. As shown in FIG. 19a and FIG. 19b, in the light-emitting mechanism portion formed on the main surface of the light guide material including the acrylic cast plate by laser etching, irregularities of several μm order are observed on the surface, and It can be seen that bubbles of several μm in the cross section exist locally in the vicinity of the inclined surface and are enclosed. In other words, the foamed surface layer 244 is a layer having a fine structure having a crack-generating shape, a concave-pore shape, or a hollow-inclusive shape, and is a layer containing bubbles in the above-described fine structure. On the other hand, as shown in Fig. 19c and Fig. 19d, the light-emitting mechanism portion formed on the main surface of the acrylic extrusion plate by laser etching has a smooth surface, and it is understood that bubbles are not present in the cross section.

Here, the comparison of the light guide samples B11 and B12 is shown. However, the same tendency was observed in the comparison of the light guide samples B9 and B10 and the comparison of the light guide samples B13 and B14.

[Evaluation Results of Examples 5 to 7 and Comparative Examples 5 to 7]

20 is a graph showing the luminance distribution at each emission angle of the light guide body of the light guide samples B9 and B10 obtained in Example 5 and Comparative Example 5. Here, in order to compare the contour of the luminance distribution, it is indicated that The value of the peak luminance is set to 1.0 to normalize the data. In addition, in the figure, the horizontal axis represents the angle of the emitted light, the vertical axis represents the relative luminance at the angle, and the direction of the light incident end face observed from the light exiting means is represented by - (negative), and the opposite is indicated by + (positive). direction. As shown in FIG. 20, in any of the light guide samples B9 and B10, the inclination angle of the inclined surface of the concave portion 101 and the foamed surface layer 244 which constitute the V-groove longitudinal section of the light-emitting means can be used. The α is controlled at around 25 degrees, and an exit profile having an exit peak near 40 degrees is obtained. However, it can be seen that the light guide sample B10 is emitted sharply in the vicinity of the emission peak angle, and a highly directivity profile is exhibited. On the other hand, the light guide sample B9 of the embodiment of the present invention has a broad emission profile, especially at the light incidence. The end face side is widely emitted. The reason for this is that, in the light guide sample B9, the fine bubbles are partially enclosed in the vicinity of the inclined surface of the light incident end surface side of the foamed surface layer 244 of the light-emitting mechanism portion, and the light propagating in the light guide body is effectively The scattering side emerges.

FIG. 21 is a graph showing the luminance distribution at each emission angle when the two light-emitting surfaces of the light guide samples B9 and B10 obtained in the example 5 and the comparative example 5 are arranged on the light-emitting surface side. As shown in the figure, in any of the light guides, the peaks of the emitted light can be raised in the normal direction by using two cymbals, but if the exit profiles of the two are compared, the light guide samples are The B9 achieves a broad exit profile compared to the B10.

Table 3 below is a table showing an angular range (80% peak angle range) of values equal to or greater than 80% (relative brightness = 0.8) of the peaks in the respective emission profiles of Fig. 21 . As shown in Table 3, the 80% peak angle range of the surface light source device using the light guide sample B10 was only 22.8 degrees, whereas the 80% peak angle range of the surface light source device using the light guide sample B9 was expanded to 30.5. As described above, it has been found that by using the light guide body as the embodiment of the present invention, an emission profile having a peak in the vicinity of the normal direction of the light exit surface can be obtained without using a diffusion sheet, and a surface light source device having a wide viewing angle can be obtained.

Fig. 22 is a graph showing the luminance distribution at each emission angle in the light guide body of the light guide samples B11 and B12 obtained in Example 6 and Comparative Example 6. Here, the value of the luminance is the same as described above, and the value of the peak luminance is set to 1.0 to normalize. As shown in FIG. 22, in any of the light guide samples B11 and B12, the inclination angle α of the inclined surface of the concave portion 101 and the foamed surface layer 244 which constitute the V-groove cross section of the light-emitting means can be used. The control is near 45 degrees, and an exit profile having an exit peak near 30 degrees is obtained. However, it can be seen that the light guide sample B12 is emitted sharply in the vicinity of the emission peak angle, and a highly directivity profile is exhibited. On the other hand, the light guide sample B11 of the embodiment of the present invention has a broad emission profile, especially at the light incidence. The end face side is widely emitted. The reason for this is that, in the light guide sample B11, the fine bubbles are partially enclosed in the vicinity of the inclined surface of the light incident end surface side of the foamed surface layer 244 of the light-emitting mechanism portion, and the light propagating inside the light guide body is effectively The scattering side emerges.

FIG. 23 is a view showing the respective exit angles when the wafers 230 having the arrays of the arrays of the light guide samples B11 and B12 obtained in the example 6 and the comparative example 6 are arranged in parallel with the light incident end surface. The brightness distribution underneath. As shown in the figure, in any of the light guides, the peak of the emitted light can be raised in the normal direction by using one of the cymbals 230, but the light guide is compared when the exit profiles of the two are compared. Sample B11 achieved a broad exit profile compared to B12.

Table 4 below is a table showing an 80% peak angle range in each of the emission profiles of Fig. 23. As shown in Table 4, the 80% peak angle range of the surface light source device using B12 is only 38.5 degrees. On the other hand, the 80% peak angle range of the surface light source device using B11 is expanded to 46.0 degrees, and it is known that According to the light guide of the embodiment of the present invention, even if a diffusion sheet and a cymbal having a line perpendicular to the light incident end surface are used, an emission profile having a peak near the normal direction of the light exit surface can be obtained. A surface light source device with a wide viewing angle.

Fig. 24 is a graph showing the luminance distribution at each emission angle of the light guide body of the light guide samples B13 and B14 obtained in Example 7 and Comparative Example 7. Here, the value of the luminance is the same as described above, and the value of the peak luminance is set to 1.0 to normalize. As shown in FIG. 24, in any of the light guide samples B13 and B14, the inclination angle α of the inclined surface of the concave portion 101 and the foamed surface layer 244 which constitute the V-groove cross section of the light-emitting means can be used. The control is near 63 degrees, and an exit profile having an exit peak near -10 degrees is obtained. However, it is understood that the light guide sample B13 which is an embodiment of the present invention has a wider emission profile than the light guide sample B14, and is particularly broadly emitted on the side opposite to the light incident end face. The reason for this is that, in the light guide sample B13, the fine bubbles are partially enclosed in the vicinity of the inclined surface of the light incident end surface side of the foamed surface layer 244 of the light-emitting mechanism portion, and the light propagating inside the light guide body is effectively The scattering side emerges.

Therefore, it is understood that the diffusing film and the cymbal sheet can be used, and an emission profile having a peak in the vicinity of the normal direction of the light exit surface can be obtained in the light guide body, and a surface light source device having a wide viewing angle can be obtained.

According to the results of the above-described Examples 1 to 7 and Comparative Examples 1 to 7, it is shown that the peak of the emitted light is controlled in an arbitrary direction by using the light guide for the surface light source device of the present invention, and the viewing angle can be obtained. A wide range of surface light source devices with good light quality.

1, 1'. . . Annular band

2, 2', 3, 3'. . . Main pulley

4. . . Roll

5. . . Slurry supply tube

6. . . Gasket

7, 8. . . Steam line

9, 10. . . Drainage line

11, 12, 13. . . Blower

14, 14'. . . Heat exchanger

15, 16, 17, 18. . . Heating zone

19. . . Plate polymer (light guide material)

22,340. . . led

twenty four. . . Light guide

26. . . Light diffusing element

28. . . First optical deflecting element

30. . . Second optical deflecting element

32. . . Light reflecting element

101. . . Concave (light exit mechanism)

110, 242, 304. . . Light exit surface

120, 241, 302. . . Light incident end face

130, 243, 303. . . back

220. . . Diffusion sheet

230, 240. . . Bract

244. . . Foaming surface layer

301. . . Foamed surface layer (light exit mechanism)

310. . . A reflective sheet

350. . . Constant current power supply

360. . . Luminance meter

401. . . Supply mold

402. . . Ultraviolet polymerizable viscous liquid (slurry)

402'. . . Acrylic cast plate (light guide material)

404. . . Ultraviolet irradiation device

408. . . Upper surface pressing roller

408'. . . Lower surface pressing roller

410. . . Hot air heating device

413. . . First film

414, 417. . . Feeding device

415, 418. . . Winding device

416. . . Second film

A1, A9. . . Light guide material

B1, B9. . . Light guide for surface light source device

α. . . slope

Fig. 1 is a schematic configuration diagram showing an embodiment of a surface light source device according to the present invention.

Fig. 2 is a schematic partial cross-sectional view showing a light guide body in the surface light source device of Fig. 1;

Fig. 3 is a SEM plan view showing a foamed surface layer formed on the back surface of a light guide of the surface light source device of Fig. 1;

4 is a SEM cross-sectional perspective view showing a foamed surface layer formed on a back surface of a light guide of the surface light source device of FIG. 1.

FIG. 5 is a schematic configuration diagram showing an example of an apparatus for manufacturing a plate-shaped light guide material used in the production of the light guide for a surface light source device of the present invention.

Fig. 6 is a SEM plan view of a laser-etched portion including a light guide material of an acrylic resin sheet obtained by extrusion molding, which is shown in comparison with Fig. 3 .

Fig. 7 is a SEM cross-sectional perspective view of a laser-etched portion including a light guide material of an acrylic resin sheet obtained by extrusion molding, which is shown in comparison with Fig. 4 .

8a and 8b are schematic views showing a light guide for a surface light source device.

FIG. 9 is an explanatory diagram of a method of evaluating optical characteristics (brightness distribution) of the surface light source device.

FIG. 10 is an explanatory diagram of a method of evaluating optical characteristics (light-emitting quality) of the surface light source device.

FIG. 11 is a schematic configuration diagram showing an example of an apparatus for manufacturing a plate-shaped light guide material used in the production of the light guide for a surface light source device of the present invention.

FIG. 12 is a view showing observation results of concave portions of the light-emitting means of the light guide for a surface light source device obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

FIG. 13 is a graph showing the luminance distribution at each emission angle of the light guide body of the light guide for a surface light source device obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

FIG. 14 is a view showing an observation result of a concave portion of the light-emitting means of the light guide for a surface light source device obtained in Example 4 and Comparative Example 4.

FIG. 15 is a graph showing the luminance distribution at each emission angle of the light guide body of the light guide for a surface light source device obtained in Example 4 and Comparative Example 4. FIG.

16a and 16b are schematic views showing a light guide for a surface light source device.

Fig. 17 is an explanatory diagram of a method of evaluating optical characteristics of a surface light source device.

FIG. 18 is a view showing the results of observation and evaluation of the concave portion of the light-emitting means of the light guide for a surface light source device obtained in Examples 5 to 7 and Comparative Examples 5 to 7.

19a to 19d are views showing SEM observation results of concave portions of the light-emitting means of the light guide for a surface light source device obtained in Example 6 and Comparative Example 6.

FIG. 20 is a graph showing the luminance distribution at each emission angle in the light guide body of the light guide samples B9 and B10 obtained in Example 5 and Comparative Example 5. FIG.

FIG. 21 is a graph showing the luminance distribution at each emission angle when the two light-emitting surfaces of the light guide samples B9 and B10 obtained in the example 5 and the comparative example 5 are arranged on the light-emitting surface side.

Fig. 22 is a graph showing the luminance distribution at each emission angle in the light guide body of the light guide samples B11 and B12 obtained in Example 6 and Comparative Example 6.

FIG. 23 is a graph showing the luminance distribution at each emission angle when one wafer is disposed on the light-emitting surface side of the light guide samples B11 and B12 obtained in Example 6 and Comparative Example 6. FIG.

Fig. 24 is a graph showing the luminance distribution at each emission angle of the light guide body of the light guide samples B13 and B14 obtained in Example 7 and Comparative Example 7.

twenty four. . . Light guide

242. . . Light exit surface

243. . . back

244. . . Foaming surface layer

α. . . slope

Claims (11)

A light guide for a surface light source device comprising a light incident end surface, a light exit surface, and a plate-shaped light guide body located on a back surface opposite to the light exit surface, wherein the light exit surface and the back surface In at least one of the regions, a concave portion is formed in at least a portion of the region, and at least one of the light emitting surface and the back surface is formed with a foamed surface layer in at least a portion of the region, and the foamed surface layer contains bubbles. The cross section including the direction of the normal to the light exit surface or the back surface is concave, and the foamed surface layer is partially present in the vicinity of the surface of the concave portion, and the diameter of the bubbles contained in the foamed surface layer is 1 μm to 50 μm. But does not include 1μm. The light guide for a surface light source device according to claim 1, wherein the foamed surface layer has a thickness of from 1 μm to 50 μm. The light guide for a surface light source device according to claim 1, wherein the region in which the portion of the foamed surface layer is formed includes a dot-like region of one of the light exit surface and the back surface. The light guide for a surface light source device according to claim 1, wherein the region in which the portion of the foamed surface layer is formed includes a stripe region in one of the light exit surface and the back surface. The light guide for a surface light source device according to claim 1, wherein the foamed surface layer and a portion other than the foamed surface layer of the light guide include an acrylic resin. A surface light source device comprising the light guide for a surface light source device according to any one of claims 1 to 5, and a primary light source disposed adjacent to a light incident end surface of the light guide. And formed. The surface light source device according to claim 6, wherein the surface light source device further includes a light reflecting element disposed adjacent to a rear surface of the light guiding body. The surface light source device according to claim 6, wherein the surface light source device further includes a light deflecting element disposed adjacent to a light emitting surface of the light guiding body. The surface light source device according to claim 8, wherein the light deflecting element includes a light incident surface that is closer to the light guide body and a light emitting surface that is opposite to the light incident surface, and the light emitting surface is It is formed by including a plurality of columns arranged in parallel with each other. A method of producing a light guide for a surface light source device according to any one of claims 1 to 5, wherein the method of manufacturing a light guide for a surface light source device according to any one of claims 1 to 5, wherein Forming a plate-shaped light guide material including an acrylic plate; and performing laser etching on a region of at least a portion of at least one main surface of the plate-shaped light guide material, thereby forming the foamed surface layer . The method of manufacturing a light guide for a surface light source device according to claim 10, wherein the laser used in the laser etching is an infrared laser.